Marking someone as 'end of line' in a tree ?

What's the normal convention for recording someone as 'being without issue' in genealogy terms ?

I'm thinking here of looking at a large family (14 children), some of whom married and had children, some of whom remained single, joined religious orders, etc . . .

When looking at the tree (one branch of many) it can be hard to tell whether someone actually was confirmed as having no children or whether I just haven't managed to research them properly yet.

In other words, what's the normal convention for showing that research is complete on that line ? I know I can add in notes to their person record to that effect, but the notes are a bit free form and I was thinking that logically there might be some way to flag it distinctly.

Within GRAMPS I can lock a record, presumably with the aim of indicating that the individual is complete, but is there another mechanism ?

Thanks,

z